Reduced moisture pickup in polyol-containing mineral filler products

ABSTRACT

The present invention relates to a process for the production of a mineral filler product comprising a step of dry grinding a calcium carbonate-containing material in the presence of an agent being a polyol. The mineral filler product according to the present invention was found to have a reduced moisture pickup as compared to prior art products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/128,702, filed Sep. 23, 2016, which is the U.S. national phase of PCTApplication No. PCT/EP2015/058141, filed Apr. 15, 2015, which claimspriority to U.S. Provisional Application No. 62/042,871, filed Aug. 28,2014 and European Application No. 14164989.7, filed Apr. 16, 2014, thecontents of which are hereby incorporated by reference.

The present invention relates to a combination of a dry grinding andclassification process for the production of a mineral filler producthaving a reduced moisture pickup.

In general, mineral filler products may be used in a multitude ofapplications, for example in polymer compositions (e.g., polyolefinfilms), in paper making, paper coatings, agricultural applications,paints, adhesives, sealants, construction applications, or cosmeticapplications.

Well-known mineral fillers comprise, for example, natural ground calciumcarbonate (GCC) and precipitated calcium carbonate (PCC).

For the preparation of ground calcium carbonate it has been quite commonto use agents, such as grinding agents or dispersing agents, in order toimprove the grinding and/or dispersing efficiency. Such agents may beselected, for example, from polymers such as polyalkylene glycols (e.g.,polyethylene glycol). Some publications also describe monomeric polyols(e.g., ethylene glycol, propylene glycol or glycerol etc.) to besuitable as grinding or dispersing agents, especially during drygrinding.

In EP 2 029 677, a process for dry grinding a material containing acarbonate ore is described, said process includes the steps of drygrinding said material in at least one grinding unit in the presence ofat least one polyalkylene glycol polymer in such manner that thequantity of water in the grinding unit is less than 10.0 wt.-%, based onthe dry material in said grinding unit. The process may further comprisean optional classifying step, wherein both the grinding step and thelatter classifying step may be carried out repeatedly with all or partof the material obtained in the dry grinding step and/or in theclassifying step.

EP 2 132 268 provides a method for dry grinding of one or more mineralmaterials which include at least one calcium carbonate. The methodincludes the steps of crushing the mineral material(s) in at least onecrushing unit, dry grinding the crushed material in at least onegrinding unit in the presence of a comb-type hydrophilic polymercontaining at least one polyalkylene oxide, wherein the quantity ofliquid in the grinding unit is less than 15.0 wt.-%, based on the drymaterial crushed in said crushing unit. The process may further comprisean optional classifying step, wherein both the grinding step and thelatter classifying step may be carried out repeatedly with all or partof the material obtained in the dry grinding step and/or in theclassifying step.

WO 2011/077232 relates to the use of formulations containing glyceroland/or polyglycerols as an agent during dry grinding to improve theself-dispersing properties of said mineral material in an aqueouscomposition. The viscosity of the final composition is thus reduced andkept stable over time. Furthermore, the amount of foam formed during thedispersing step is reduced.

WO 2011/070418 relates to a method for classifying mineral material,using a classification assisting additive that contains glycerol and/orat least one polyglycerol and allows air classification effectiveness tobe increased or uses less specific classification energy thanadditive-free air classification, while obtaining a classified mineralmaterial that is compatible with use in an aqueous medium. The inventionalso relates to the use of the resulting product in paints, plastics,food and feed, pharmaceutical formulations, paper mass and papercoatings.

Attempts have also been made to improve the applicability of mineralfiller products and especially calcium carbonate-containing mineralfiller products, e.g., by treating particulate calcium carbonates withhigher aliphatic carboxylic acids, which in some cases may also bereferred to as fatty acids, and aliphatic carboxylic acid salts.

For instance, WO 00/20336 relates to an ultrafine natural calciumcarbonate which may optionally be treated with one or more several fattyacids or one or more several salts, or mixtures thereof, and which isused as a rheology regulator for polymer compositions.

Likewise, U.S. Pat. No. 4,407,986 relates to a precipitated calciumcarbonate that is surface treated with a dispersant that may includehigher aliphatic acids and their metal salts in order to limit theaddition of lubricant additives when kneading this calcium carbonatewith crystalline polypropylene and to avoid the formation of calciumcarbonate aggregates that limit the impact strength of thepolypropylene.

In EP 0 325 114 relating to non-sagging underseal compositions for motorvehicles based on polyvinyl chloride which has improved rheological andadhesion properties, a mixture of an ammonium salt of 12-hydroxystearicacid in combination with a fatty acid (in a weight ratio of 1:1) is usedto treat a mineral filler.

German patent DE 958 830 relates to a process for the treatment ofnatural calcium carbonate in the presence of, for example, fatty acids,fatty alcohols, and fatty amides which are used as a dry grinding aid inorder to avoid formation of filler adhesions on the grinding chamberwall.

Unpublished European patent application No. 12 188739.2 relates to aprocess for preparing a surface treated filler material product withmonosubstituted succinic anhydride(s) and, optionally, withmonosubstituted succinic acids.

Moreover, particulate mineral materials may also be treated with othersurface treatment agents, such as silanes, siloxanes, phosphates,phosphonates, oxalates, fluorides, or mixtures thereof in order tohydrophobize the surface of said mineral material.

In many cases, the preparation of calcium carbonate-containing mineralfiller products by use of the aforementioned grinding and treatmentagents leads to a poor quality. For example, the use of agents, such asmonomeric polyols or polyalkylene glycols, often results in a highmoisture pick up susceptibility of the resulting mineral filler product.The use of particulate calcium carbonate-containing materials havinghigh moisture pick up susceptibilities may be disadvantageous when usedas a filler in polymer compositions. For example, such materials maypick up moisture during storage, transportation, and processing which,in turn, may lead to the formation of voids in polymer compositionsproduced in a melt extrusion process.

In view of the foregoing, the expert is still faced with the problem ofefficient production of dry ground fillers for the application inplastics, such as polyolefins, without a decrease in quality. Forexample, the absence of grinding agents and dispersants in dry grindingoperations results in a low throughput and low grinding efficiencywhich, in turn, leads to an overall increase in energy consumption.

Therefore, there is still a need to provide mineral filler products andprocesses for their preparation which may reduce or avoid one or more ofthe aforementioned technical drawbacks.

It is thus an object of the present invention to provide a process forthe preparation of a mineral filler product which may be carried underhigh throughput and at high grinding efficiency. Another object may alsobe seen in the provision of a more efficient dry grinding process forthe provision of a mineral filler product having a reduced moisture pickup.

One or more of the foregoing and other problems are solved by thesubject-matter as defined herein in the independent claims.

A first aspect of the present invention relates to a process for thepreparation of a mineral filler product, the process comprising thesteps of:

-   -   (a) providing a calcium carbonate-containing material;    -   (b) providing at least one agent being a polyol;    -   (c) dry grinding the calcium carbonate-containing material in a        mixture comprising:        -   (i) the calcium carbonate-containing material provided in            step (a); and        -   (ii) the at least one agent provided in step (b) in at least            one grinding unit to obtain a dry ground calcium            carbonate-containing material;    -   (d) classifying the dry ground calcium carbonate-containing        material of step (c) to obtain one or more coarse fractions and        one or more fine fractions, wherein one or more of the coarse        fractions are removed and/or subjected to dry grinding step (c)        and/or subjected to classifying step (d); and    -   (e) treating the calcium carbonate-containing material before        and/or during and/or after step (c) with at least one        monosubstituted succinic anhydride and, optionally, with at        least one monosubstituted succinic acid and/or salt(s) thereof,        to obtain a calcium carbonate-containing material having a        treatment layer on at least part of the surface of said        material;    -   wherein the total amount of the at least one agent provided in        step (b) ranges from 0.01 to 5.0 wt.-%, based on the total dry        weight of the calcium carbonate-containing material provided in        step (a);    -   the total moisture content in the mixture of step (c) is less        than or equal to 5.0 wt.-%, based on the total weight of said        mixture;    -   the total amount of the at least one monosubstituted succinic        anhydride and the optional at least one monosubstituted succinic        acid and/or salt(s) thereof in step (e) ranges from 0.01 to 5.0        wt.-%, based on the total dry weight of the calcium        carbonate-containing material provided in step (a); and    -   the temperature in step (e) is adjusted to at least 2° C. above        the melting point of the at least one monosubstituted succinic        anhydride.

According to the process of the present invention, a mineral fillerproduct is obtained by dry grinding a calcium carbonate-containingmaterial in the presence of a polyol, for example glycerol. The dryground calcium carbonate-containing material is then classified toobtain one or more coarse fractions and one or more fine fractions. Oneor more of the coarse fractions may be removed from the process.Alternatively, one or more of the coarse fractions may be subjected todry grinding step (c), classifying step (d) or both. The processaccording to the present invention further comprises a treatment step,referred to as step (e), using a hydrophobizing agent selected from atleast one monosubstituted succinic anhydride and, optionally, at leastone monosubstituted succinic acid and/or salt(s) thereof. In saidtreatment step, a treatment layer is formed on at least part of thesurface of the calcium carbonate-containing material upon heating thecalcium carbonate-containing material together with the hydrophobizingagent. The treatment step may be carried out before and/or during and/orafter dry grinding step (c) meaning that the hydrophobizing agent iscontacted with the calcium carbonate-containing material of step (a)and/or the dry ground calcium carbonate-containing material obtainedduring or after step (c). Likewise, the hydrophobizing agent may beapplied to any of the fractions obtained in classifying step (d),preferably one or more of the fine fractions.

Another aspect of the present invention relates to a mineral fillerproduct. Said product is obtainable by the process according to thepresent invention.

It should be understood that for the purposes of the present invention,the following terms have the following meanings:

The term “filler” in the meaning of the present invention refers tosubstances which may be added to materials, such as polymers,elastomers, paints, or adhesives, e.g., to lower the consumption of moreexpensive materials or to improve material or mechanical properties ofthe resulting products. The person skilled in the art very well knowsthe fillers, typically mineral fillers, used in the respective field.

A “natural calcium carbonate source” may be any natural materialcomprising calcium carbonate. Such materials comprise, for example,calcite, marble, limestone, chalk, dolomite, and the like.

The term “polyol” as used herein refers to any organic compound beingsubstituted with at least two hydroxy groups, whereof two or morehydroxy groups are each bound to another carbon atom. It is to beunderstood that such a polyol may be monomeric (e.g., glycerol, ethyleneglycol, propylene glycol, triethanolamine, or triisopropanolamine),oligomeric (e.g., diethylene glycol, triethylene glycol, dipropyleneglycol, tripropylene glycol, diglycerol, or triglycerol), or polymeric(e.g., homo- or heteropolymers of ethylene glycol, propylene glycol, orglycerol).

The term “dry ground” or “dry grinding” in the meaning of the presentinvention refers to the comminution of a solid material by using a mill(e.g., by means of a ball mill), wherein said material to be ground hasa total moisture content of less than or equal to 5.0 wt.-%, based onthe total weight of said material.

The terms “coarse” and “fine” as used herein describe the particle sizeof two fractions of a particulate material relative to each other and,thus, do not imply a specific particle size or size range. Unlessindicated otherwise, both terms refer to the relative weight medianparticle sizes d₅₀. In this respect, the term “fine fraction” indicatesthat the weight median particle size d₅₀ of said fraction is smallerthan the weight median particle size d₅₀ of the corresponding “coarsefraction”.

Throughout the present application, the particle size of a fraction of aparticulate material is described by its particle size distribution. Thevalue d_(x) represents the diameter relative to which x % by weight ofthe particles have diameters less than d_(x). This means, for example,that the d₉₈ value (also referred to as the “topcut”) is the particlesize at which 98 wt.-% of all particles of a fraction are smaller thanthe indicated value. The d₅₀ value is thus the “weight median particlesize” at which 50 wt.-% of all particles are smaller than the indicatedparticle size. Particle sizes defined within the present applicationbeing smaller than 100 μm can be determined based on measurements madeby using a Sedigraph™ 5100 instrument of Micromeritics InstrumentCorporation. The method and the instrument are known to the skilledperson and are commonly used to determine the particle size of fillersand pigments. The measurements are carried out in an aqueous solution of0.1 wt.-% Na₄P₂O₇. Samples are dispersed using a high speed stirrer andsupersonics. In case of surface-treated products, additional 0.5 g of asurfactant (Photo-Flo 200® from Kodak) are added to 50 ml of thesolution of 0.1 wt.-% Na₄P₂O₇ before dispersing the treated carbonatesample. In case of particle sizes being larger than 100 μm, fractionalsieving according to the ISO 3310-1:2000 standard is used to determineparticle size distributions.

The term “succinic anhydride”, also called dihydro-2,5-furandione,succinic acid anhydride or succinyl oxide, has the molecular formulaC₄H₄O₃ and is the acid anhydride of succinic acid.

The term “monosubstituted succinic anhydride” in the meaning of thepresent invention refers to a succinic anhydride substituted with onesubstituent (R):

The term “monosubstituted succinic acid” in the meaning of the presentinvention refers to a succinic acid substituted with one substituent(R):

The “total moisture content” of a material refers to the percentage ofmoisture (i.e. water) which may be desorbed from a sample upon heatingto 220° C. The total moisture contents as defined herein can be measuredaccording to the Karl Fischer coulometric titration method, desorbingthe moisture in an oven at 220° C. for 10 min and passing itcontinuously into a KF coulometer (Mettler Toledo coulometric KFTitrator C30, combined with Mettler oven DO 0337) using dry nitrogen at100 ml/min for 10 min. A calibration curve using water has to berecorded and a blank of 10 min nitrogen flow without a sample has to betaken into account.

The “melting point” of all compounds referred to herein can be measuredwith an OptiMelt MPA100 device from SRS Stanford Research Systems,Sunnyvale, USA.

The “moisture pick up susceptibility” of a material refers to the amountof moisture absorbed on the surface of said material within a certaintime upon exposure to a defined humid atmosphere and is expressed inmg/g. The “normalized moisture pick up susceptibility” of a materialalso refers to the amount of moisture absorbed on the surface of saidmaterial within a certain time upon exposure to a defined humidatmosphere and is expressed in mg/m². The moisture pick upsusceptibility can be determined in mg moisture/g after exposure to anatmosphere of 10 and 85% relative humidity, respectively, for each 2.5 hat a temperature of +23° C. (±2° C.). For this purpose, the sample isfirst kept at an atmosphere of 10% relative humidity for 2.5 h, then theatmosphere is changed to 85% relative humidity at which the sample iskept for another 2.5 hours. The weight increase between 10 and 85%relative humidity is then used to calculate the moisture pick-up in mgmoisture/g of sample. The moisture pick up susceptibility in mg/gdivided by the specific surface area in m² (BET method) corresponds tothe normalized moisture pick up susceptibility expressed in mg/m² ofsample.

Throughout the present document, the “specific surface area” (expressedin m²/g) of a mineral filler is determined using the BET method (usingnitrogen as adsorbing gas), which is well known to the skilled person(ISO 9277:1995). The total surface area (in m²) of the mineral fillercan be obtained by multiplication of the specific surface area (in m²/g)and the mass (in g) of the mineral filler.

Where an indefinite or definite article is used when referring to asingular noun, e.g., “a”, “an” or “the”, this includes a plural of thatnoun unless anything else is specifically stated.

Where the term “comprising” is used in the present description andclaims, it does not exclude other elements. For the purposes of thepresent invention, the term “consisting of” is considered to be apreferred embodiment of the term “comprising”. If hereinafter a group isdefined to comprise at least a certain number of embodiments, this isalso to be understood to disclose a group, which preferably consistsonly of these embodiments.

Terms like “obtainable” or “definable” and “obtained” or “defined” areused interchangeably. This, e.g., means that, unless the context clearlydictates otherwise, the term “obtained” does not mean to indicate that,e.g., an embodiment must be obtained by, e.g., the sequence of stepsfollowing the term “obtained” though such a limited understanding isalways included by the terms “obtained” or “defined” as a preferredembodiment.

Whenever the terms “including” or “having” are used, these terms aremeant to be equivalent to “comprising” as defined hereinabove.

Advantageous embodiments of the process according to the presentinvention and embodiments of the mineral filler product obtainable bythe process according to the present invention are defined in thecorresponding subclaims.

According to one embodiment, the calcium carbonate-containing materialprovided in step (a) is selected from natural calcium carbonate sourcesand preferably is selected from the group consisting of calcite, marble,limestone, chalk, dolomite, and mixtures thereof.

According to another embodiment, the at least one agent provided in step(b) is a polyol selected from the group consisting of saccharides,glycerol, polyglycerol, ethylene glycol, propylene glycol, oligomers andpolymers of ethylene glycol and/or propylene glycol, andtriisopropanolamine, preferably said at least one agent is a polyolselected from glycerol and triisopropanolamine.

According to still another embodiment, the total amount of the at leastone agent provided in step (b) ranges from 0.05 to 3.0 wt.-%, preferablyfrom 0.1 to 2.0 wt.-%, and more preferably from 0.15 to 1.5 wt.-%, basedon the total dry weight of the calcium carbonate-containing materialprovided in step (a).

According to still another embodiment, the total moisture content in themixture of step (c) is less than or equal to 2.0 wt.-%, preferably lessthan or equal to 1.5 wt.-%, and more preferably less than or equal to1.0 wt.-%, based on the total weight of said mixture.

According to one embodiment, the at least one monosubstituted succinicanhydride of step (e) consists of succinic anhydride monosubstitutedwith an aliphatic group having a total amount of carbon atoms from C2 toC30, preferably from C3 to C25, and most preferably from C4 to C20.

According to another embodiment, the at least one monosubstitutedsuccinic anhydride of step (e) is at least one alkyl monosubstitutedsuccinic anhydride, preferably at least one alkyl monosubstitutedsuccinic anhydride selected from the group consisting of ethylsuccinicanhydride, propylsuccinic anhydride, butylsuccinic anhydride,triisobutyl succinic anhydride, pentylsuccinic anhydride, hexylsuccinicanhydride, heptylsuccinic anhydride, octylsuccinic anhydride,nonylsuccinic anhydride, decyl succinic anhydride, dodecyl succinicanhydride, hexadecanyl succinic anhydride, and octadecanyl succinicanhydride.

According to another embodiment, the at least one monosubstitutedsuccinic anhydride of step (e) is at least one alkenyl monosubstitutedsuccinic anhydride, preferably at least one alkenyl monosubstitutedsuccinic anhydride selected from the group consisting of ethenylsuccinicanhydride, propenylsuccinic anhydride, butenylsuccinic anhydride,triisobutenyl succinic anhydride, pentenylsuccinic anhydride,hexenylsuccinic anhydride, heptenylsuccinic anhydride, octenylsuccinicanhydride, nonenylsuccinic anhydride, decenyl succinic anhydride,dodecenyl succinic anhydride, hexadecenyl succinic anhydride, andoctadecenyl succinic anhydride.

According to still another embodiment, the temperature during step (e)ranges from 30° C. to 200° C., preferably from 80° C. to 150° C., andmore preferably from 110° C. to 130° C.

According to still another embodiment, the temperature in step (e) isadjusted to at least 2° C. above the melting point of the at least onemonosubstituted succinic anhydride for less than 1 h, preferably lessthan 5 min, more preferably less than 1 min, and most preferably 1 to 10s.

According to another embodiment, the total amount of the at least onemonosubstituted succinic anhydride and the optional at least onemonosubstituted succinic acid and/or salt(s) thereof in step (e) rangesfrom 0.05 to 3.0 wt.-%, preferably from 0.1 to 2.0 wt.-%, and morepreferably from 0.15 to 1.5 wt.-%, based on the total dry weight of thecalcium carbonate-containing material provided in step (a).

According to another embodiment, said treatment layer of step (e)comprises the at least one monosubstituted succinic anhydride and/orreaction product(s) thereof and the optional at least onemonosubstituted succinic acid and/or salt(s) thereof and/or reactionproduct(s) thereof in a total amount of from 0.01 to 2.0 wt.-%,preferably from 0.05 to 1.5 wt.-%, and more preferably from 0.1 to 1.0wt.-%, based on the total dry weight of the calcium carbonate-containingmaterial.

According to still another embodiment, the mineral filler product has aweight median particle size d₅₀ ranging from 0.3 to 25.0 μm, preferablyfrom 0.5 to 10.0 μm, more preferably from 1.0 to 8.0 μm, and mostpreferably from 1.2 to 5.0 μm.

According to still another embodiment, the mineral filler product has aspecific surface area ranging from 0.5 to 20.0 m²/g, preferably from 1.0to 10.0 m²/g, and more preferably from 2.0 to 8.0 m²/g as measured bythe BET nitrogen method.

The process according to the present invention comprises the steps ofdry grinding a calcium carbonate-containing material in the presence ofan agent being a polyol and a step of treating the calciumcarbonate-containing material with at least one monosubstituted succinicanhydride and, optionally, with at least one monosubstituted succinicacid and/or salt(s) thereof.

The inventors surprisingly found that the mineral filler productobtainable by the process according to the present invention providesseveral advantages. Accordingly, the problems described hereinabove withrespect to the prior art may be solved by the process according to thepresent invention using an agent selected from polyols which may be seenas a grinding or dispersing agent together with a hydrophobizing agentas defined herein in the claims. The use of a polyol during dry grindingstep (c) may result in higher mill capacities and a higher throughputwhich requires lower investments and smaller plant footprints for equalproduction capacities.

It was further found that the specific combination of an agent being apolyol during dry grinding together with at least one monosubstitutedsuccinic anhydride used in a treatment step is of particular advantage.

The treatment layer formed in said treatment step leads to a moisturepick up (measured as the moisture pickup susceptibility) of the finalmineral filler product which is significantly reduced as compared toprior art treatment methods using, for example, stearic acid.

Calcium carbonate-containing materials showing a reduced moisture pickup may be particularly suitable as a filler in polymer compositions.Such fillers do not significantly pick up moisture during storage,transportation, and/or processing which, in turn, may lead to reducedvoid formation in polymer compositions produced, for example, in a meltextrusion process.

In the following, preferred embodiments of the process according to thepresent invention for the preparation of a mineral filler product willbe discussed in more detail.

It is to be understood that these details and embodiments also apply tothe mineral filler product itself.

Step (a)—the Calcium Carbonate-Containing Material

According to step (a) of the process according to the present invention,a calcium carbonate-containing material is provided. In general, saidcalcium carbonate-containing material may be any calcium carbonatesource and may be of natural or synthetic origin.

In some embodiments of the process according to the present invention,the calcium carbonate-containing material provided in step (a) isselected from natural calcium carbonate sources, preferably containingfrom 50.0 to 99.9 wt.-% of calcium carbonate, based on the total dryweight of said calcium carbonate-containing material.

According to one embodiment, the calcium carbonate-containing materialprovided in step (a) contains at least 50.0 wt.-%, preferably at least70.0 wt.-%, more preferably at least 80.0 wt.-%, even more preferably atleast 90.0 wt.-%, and most preferably from 90.0 to 99.9 wt.-% of calciumcarbonate, based on the total dry weight of said calciumcarbonate-containing material.

According to another embodiment, the calcium carbonate-containingmaterial provided in step (a) is selected from the group consisting ofcalcite, marble, limestone, chalk, dolomite, and mixtures thereof.

According to a preferred embodiment, the calcium carbonate-containingmaterial provided in step (a) is selected from the group consisting ofcalcite, marble, limestone, chalk, and mixtures thereof.

In cases where the calcium carbonate is of synthetic origin, the calciumcarbonate-containing material may be precipitated calcium carbonate(PCC). PCC in the meaning of the present invention is a synthesizedmaterial, generally obtained by precipitation following a reaction ofcarbon dioxide and calcium hydroxide (hydrated lime) in an aqueousenvironment or by precipitation of a calcium- and a carbonate source inwater. Additionally, precipitated calcium carbonate can also be theproduct of introducing calcium and carbonate salts, calcium chloride andsodium carbonate, for example, in an aqueous environment. PCC may bevaterite, calcite or aragonite. PCCs are described, for example, in EP 2447 213, EP 2 524 898, EP 2 371 766.

Suitably, the calcium carbonate-containing material of step (a) isprovided as a solid material being in particulate form. In this respect,the calcium carbonate-containing material provided in step (a) may haveany particle size distribution allowing the material to be subjected toa dry grinding step. Therefore, the calcium carbonate-containingmaterial may be provided as a comminuted material, for example, incrushed or preground form.

According to one embodiment, the calcium carbonate-containing materialprovided in step (a) may have a weight median particle size d₅₀ rangingfrom 5.0 to 600.0 μm, preferably from 10.0 to 500.0 μm, and morepreferably from 50.0 to 300.0 μm.

In some embodiments of the present invention, the calciumcarbonate-containing material may also have a specific total moisturecontent.

According to one embodiment, the calcium carbonate-containing materialprovided in step (a) has a total moisture content of from 0.01 to 1.0wt.-%, preferably from 0.02 to 0.5 wt.-%, more preferably from 0.03 to0.2 wt.-%, and most preferably from 0.05 to 0.1 wt.-%, based on thetotal dry weight of the calcium carbonate-containing material.

If necessary, the total moisture content of the calciumcarbonate-containing material provided in step (a) can be adjusted, forexample by drying, to specific values (e.g., the values specified above)prior to subjecting same to dry grinding step (c).

Step (b)—the Polyol Agent

According to step (b) of the process according to the present invention,an agent being a polyol is provided.

Said agent provided in step (b) serves as an additive to improve thegrinding properties and also serves to avoid the formation ofagglomerates which may lead to a poor separation accuracy in thesubsequent classifying step.

As already described hereinabove, a polyol in the meaning of the presentinvention may be any organic compound being substituted with at leasttwo hydroxy groups, whereof two or more hydroxy groups are each bound toanother carbon atom. It is to be understood that such a polyol may bemonomeric (e.g., glycerol, ethylene glycol, propylene glycol, ortriisopropanolamine), oligomeric (e.g., diethylene glycol, triethyleneglycol, dipropylene glycol, or tripropylene glycol), or polymeric (e.g.,homo- or heteropolymers of ethylene glycol, propylene glycol, orglycerol).

Therefore, in one embodiment, the polyol of step (b) is an organiccompound being substituted with at least two hydroxy groups, whereof twoor more hydroxy groups are each bound to another carbon atom.

According to another embodiment, the polyol of step (b) is a monomericpolyol, preferably a monomeric organic compound being substituted withat least two hydroxy groups, whereof two or more hydroxy groups are eachbound to another carbon atom.

In another embodiment, the polyol of step (b) is an oligomeric orpolymeric polyol, preferably an oligomeric or polymeric organic compoundbeing substituted with at least two hydroxy groups, whereof two or morehydroxy groups are each bound to another carbon atom.

In cases where the polyol of step (b) is an oligomeric or polymericpolyol, said polyol may be selected from homooligomers, heterooligomers,homopolymers, or heteropolymers of ethylene glycol, propylene glycol, orglycerol.

However, in many embodiments the polyol may be independently selectedfrom monomeric, oligomeric, or polymeric polyols.

According to one embodiment, the at least one agent provided in step (b)is a polyol selected from the group consisting of saccharides, glycerol,polyglycerol, ethylene glycol, propylene glycol, oligomers and polymersof ethylene glycol and/or propylene glycol, and triisopropanolamine.

According to another embodiment, the at least one agent provided in step(b) is a polyol selected from the group consisting of glycerol, ethyleneglycol, propylene glycol, and triisopropanolamine.

In another embodiment, the at least one agent provided in step (b) is apolyol selected from glycerol and triisopropanolamine, preferably saidat least one agent is glycerol.

Saccharides which are suitable to be used as the at least one agentprovided in step (b) may be selected from monosaccharides (e.g., glucoseand sorbitol), disaccharides (e.g., sucrose), oligosaccharides, andpolysaccharides (e.g., starch, cellulose, and derivatives of both),wherein monosaccharides and disaccharides are preferred.

Therefore, in one embodiment, the saccharides are selected frommonosaccharides and disaccharides, preferably sorbitol and saccharose.

Another requirement of the process according to the present invention isthe total amount of the at least one agent provided in step (b). Ingeneral, said total amount may range from 0.01 to 10.0 wt.-%, based onthe total dry weight of the calcium carbonate-containing materialprovided in step (a).

However, it is preferred to use relatively small amounts of said atleast one agent as large amounts of polyols may result in an increase ofthe moisture pickup.

Therefore, in one embodiment, the total amount of the at least one agentprovided in step (b) may range from 0.01 to 5.0 wt.-%, based on thetotal dry weight of the calcium carbonate-containing material providedin step (a).

In another embodiment of the inventive process, the total amount of theat least one agent provided in step (b) ranges from 0.05 to 3.0 wt.-%,preferably from 0.1 to 2.0 wt.-%, and more preferably from 0.15 to 1.5wt.-%, based on the total dry weight of the calcium carbonate-containingmaterial provided in step (a).

Step (c)—Dry Grinding

According to step (c) of the process according to the present invention,a mixture comprising the calcium carbonate-containing material providedin step (a) and the at least one agent provided in step (b) is dryground in at least one grinding unit to obtain a dry ground calciumcarbonate-containing material.

The term “dry ground” or “dry grinding” in the meaning of the presentinvention refers to the comminution of a solid material by using a mill(e.g., by means of a ball mill), wherein said material to be ground hasa total moisture content of less than or equal to 5.0 wt.-%, based onthe total weight of said material.

For the purposes of the present invention, any suitable mill known inthe art may be used, for example a ball mill, semi-autogenous mill, orautogenous mill. However, said at least one grinding unit preferably isa ball mill.

It has also to be noted that step (c) is carried out by using at leastone grinding unit, i.e. it is also possible to grind the calciumcarbonate-containing material in one or more steps by using a series orcascade of grinding units which may be selected, for example, from anyof the foregoing mill types.

The amount of water being present in the mixture to be dry ground may beexpressed by the total moisture content which is based on the totalweight of said mixture. Typically, dry grinding processes are carriedusing mixtures having a total moisture content of less than or equal to5.0 wt.-%, based on the total weight of said mixture.

However, in some cases it may also be advantageous if said mixture to beground contains traces of water meaning that the mixture may have alower total moisture content limit of, for example, 0.01, 0.02, 0.03, or0.05 wt.-%, based on the total weight of said mixture. Such traces ofwater or moisture may be useful for the formation of the treatment layerduring treatment step (e), for example by triggering the hydrolysis ofanhydride units.

According to one embodiment, the total moisture content in the mixtureof step (c) is less than or equal to 2.0 wt.-%, preferably less than orequal to 1.5 wt.-%, and more preferably less than or equal to 1.0 wt.-%,based on the total weight of said mixture, wherein the total moisturecontent in the mixture of step (c) preferably has a lower limit of 0.03wt.-%, based on the total weight of said mixture.

According to another embodiment, the total moisture content in themixture of step (c) ranges from 0.01 to 1.0 wt.-%, preferably from 0.02to 0.5 wt.-%, more preferably from 0.03 to 0.2 wt.-%, and mostpreferably from 0.05 to 0.1 wt.-%, based on the total weight of saidmixture.

Step (c) describes the dry grinding of a mixture comprising the calciumcarbonate-containing material provided in step (a) and the at least oneagent provided in step (b).

In this respect, it is possible to obtain the mixture to be ground instep (c) of the process according to the present invention by contactingwith each other the components provided in steps (a) and (b) before orduring grinding step (c). In addition, it is also possible to obtainsaid mixture by contacting with each other the components in one or moreportions before or during dry grinding step (c).

According to one embodiment, the mixture of dry grinding step (c) isobtained before said grinding step by simultaneously contacting thecalcium carbonate-containing material provided in step (a) with the atleast one agent provided in step (b). According to another embodiment,the mixture of grinding step (c) is obtained before said grinding stepby simultaneously contacting the calcium carbonate-containing materialprovided in step (a) with a first portion of the at least one agentprovided in step (b), wherein a second portion of the at least one agentis added during grinding step (c).

In one embodiment, the dry ground calcium carbonate-containing materialobtained after dry grinding step (c) has a weight median particle sized₅₀ ranging from 0.5 to 100.0 μm, preferably from 1.0 to 50.0 μm, andmore preferably from 2.0 to 20.0 μm.

In addition or alternatively to the foregoing weight median particlesizes, the dry ground calcium carbonate-containing material obtainedafter dry grinding step (c) may have a particle size topcut d₉₈ rangingfrom 1.5 to 250.0 μm, preferably from 2.0 to 130.0 μm, and morepreferably from 2.5 to 25.0 μm.

Step (d)—Classifying

Step (d) of the process according to the present invention is aclassifying step. In said classifying step, one or more coarse fractionsand one or more fine fractions are obtained, wherein one or more of thecoarse fractions are removed and/or subjected to dry grinding step (c)and/or subjected to classifying step (d).

A classifying step in general serves to divide a feed fraction having acertain particle size distribution into a coarse fraction and a finefraction each having different particle size distributions. Typically,the coarse fraction has a d₅₀ value being higher than that of the feedfraction, whereas the fine fraction has a d₅₀ value being smaller thanthat of the feed fraction.

For this purpose, screening devices as well as gravity-based devices,such as centrifuges or cyclones, and any combination of theaforementioned devices may be used. In this respect, it has to be notedthat it is also possible to use a series or cascade of any of theaforementioned classifying devices in any combination.

In one embodiment, classifying step (e) is carried out by use of one ormore cyclones. Optionally, said one or more cyclones are used incombination with one or more screens.

As defined in process step (d), one or more of the coarse fractionsobtained after classifying the calcium carbonate-containing material maybe removed and/or subjected to dry grinding step (c) and/or subjected toclassifying step (d).

In cases where one or more of the coarse fractions obtained inclassifying step (d) are subjected to dry grinding step (c) and/or againsubjected to classifying step (d), the inventive process can beconsidered as a closed circuit grinding, wherein a part or any of theone or more coarse fractions may be subjected to either one or both ofthe foregoing process steps. For example, part or any of the one or morecoarse fractions may be ground in at least one grinding unit of acascade of grinding units in step (c). Additionally or alternatively,part or any of the one or more coarse fractions may be classified in atleast one classifying device of a cascade of classifying devices in step(d).

Depending on the particle size distribution of the one or more coarsefractions, it is also possible to subject a part of the one or morecoarse fractions to classifying step (d), whereas the remaining coarsefractions are subjected to dry grinding step (c). For example, if twocoarse fractions are obtained in classifying step (d), the coarsefraction containing relatively large particles may be sent back to atleast one grinding unit of dry grinding step (c), whereas the coarsefraction containing relatively small particles may be repeatedlysubjected to classifying step (d).

In cases where one or more of the coarse fractions obtained inclassifying step (d) are removed, this means that these removed coarsefractions are recycled neither in grinding step (c) nor in classifyingstep (d). Depending on the particle size distribution of the one or morecoarse fractions, it is also possible to remove one part of the one ormore coarse fractions, whereas another part is subjected to dry grindingstep (c) and still another part of the coarse fractions is subjected toclassifying step (d). For example, if three coarse fractions areobtained in classifying step (d), the coarse fraction containing thelargest particles may be removed, whereas the coarse fraction containingmedium size particles may be sent back to the at least one grinding unitof dry grinding step (c) and the coarse fraction containing the smallestparticles may be repeatedly subjected to classifying step (d).

However, it is still possible to subject the removed coarse fractions toanother grinding step or classifying step in a parallel process stream,wherein the latter grinding and classifying steps may also include theuse of a series or cascade of the corresponding devices in one or moresteps. It is further possible to add part or all of the materialobtained in said parallel process stream to the main process streamdefined herein in the independent claim.

Alternatively, it also possible to completely remove part or all of theone or more coarse fractions obtained in classifying step (d) in a wastestream.

Depending on the order of steps (c) to (e), the one or more finefractions obtained after classifying step (e) may represent the finalproduct of the inventive process, i.e. the mineral filler product.

Therefore, according to one embodiment, the one or more fine fractionsobtained in classifying step (d) have a weight median particle size d₅₀ranging from 0.3 to 25.0 μm, preferably from 0.5 to 10.0 μm, morepreferably from 1.0 to 8.0 μm, and most preferably from 1.2 to 5.0 μm,for example from 1.5 to 1.7 μm.

In addition or alternatively to the foregoing weight median particlesizes, the one or more fine fractions obtained in classifying step (d)may have a particle size topcut d₉₈ ranging from 0.5 to 30.0 μm,preferably from 1.0 to 20.0 μm, and more preferably from 1.5 to 15.0 μm.

Step (e)—Surface Treatment

In step (e) of the process according to the present invention, thecalcium carbonate-containing material is treated before and/or duringand/or after step (c) with at least one monosubstituted succinicanhydride to obtain a calcium carbonate-containing material having atreatment layer on at least part of the surface of said material.

It is appreciated that the expression “at least one” monosubstitutedsuccinic anhydride means that one or more kinds of monosubstitutedsuccinic anhydride may be provided in the process of the presentinvention.

Accordingly, it should be noted that the at least one monosubstitutedsuccinic anhydride may be one kind of monosubstituted succinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride may be a mixture of two or more kinds of monosubstitutedsuccinic anhydride. For example, the at least one monosubstitutedsuccinic anhydride may be a mixture of two or three kinds ofmonosubstituted succinic anhydride, like two kinds of monosubstitutedsuccinic anhydride.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is one kind of monosubstitutedsuccinic anhydride.

It is appreciated that the at least one monosubstituted succinicanhydride represents a surface treatment agent and consists of succinicanhydride monosubstituted with an aliphatic group having a total amountof carbon atoms from C2 to C30 in the substituent.

The term “aliphatic group” in the meaning of the present inventionrefers a non-aromatic group containing only carbon and hydrogen.Accordingly, said term encompasses acyclic and cyclic hydrocarbons whichmay be both saturated and unsaturated. Additionally, aliphatic groups(e.g., acyclic aliphatic groups) may have a linear or branched structure(e.g., linear or branched aliphatic groups). The skilled person willthus appreciate that any branched group being part of one of theembodiments defined within this application has a total amount of carbonatoms of at least C3.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride consists of succinic anhydridemonosubstituted with an aliphatic group having a total amount of carbonatoms from C3 to C20 in the substituent. For example, the at least onemonosubstituted succinic anhydride consists of succinic anhydridemonosubstituted with an aliphatic group having a total amount of carbonatoms from C4 to C18 in the substituent.

In another embodiment of the present invention, the at least onemonosubstituted succinic anhydride consists of succinic anhydridemonosubstituted with one group being a linear aliphatic group having atotal amount of carbon atoms from C2 to C30, preferably from C3 to C20,and most preferably from C4 to C18 in the substituent.

Alternatively, the at least one monosubstituted succinic anhydrideconsists of succinic anhydride monosubstituted with one group being abranched aliphatic group having a total amount of carbon atoms from C3to C30, preferably from C3 to C20, and most preferably from C4 to C18 inthe substituent.

Thus, it is preferred that the at least one monosubstituted succinicanhydride consists of succinic anhydride monosubstituted with one groupbeing a linear or branched alkyl group having a total amount of carbonatoms from C2 to C30, preferably from C3 to C20 and most preferably fromC4 to C18 in the substituent.

For example, the at least one monosubstituted succinic anhydrideconsists of succinic anhydride monosubstituted with one group being alinear alkyl group having a total amount of carbon atoms from C2 to C30,preferably from C3 to C20, and most preferably from C4 to C18 in thesubstituent. Alternatively, the at least one monosubstituted succinicanhydride consists of succinic anhydride monosubstituted with one groupbeing a branched alkyl group having a total amount of carbon atoms fromC3 to C30, preferably from C3 to C20, and most preferably from C4 to C18in the substituent.

The term “alkyl” in the meaning of the present invention refers to alinear or branched saturated organic compound containing only carbon andhydrogen. In other words, “alkyl monosubstituted succinic anhydrides”are composed of linear or branched saturated hydrocarbon chainscontaining a pendant succinic anhydride group.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is at least one linear or branchedalkyl monosubstituted succinic anhydride. For example, the at least onealkyl monosubstituted succinic anhydride is selected from the groupconsisting of ethylsuccinic anhydride, propylsuccinic anhydride,butylsuccinic anhydride, triisobutyl succinic anhydride, pentylsuccinicanhydride, hexylsuccinic anhydride, heptylsuccinic anhydride,octylsuccinic anhydride, nonylsuccinic anhydride, decyl succinicanhydride, dodecyl succinic anhydride, hexadecanyl succinic anhydride,and octadecanyl succinic anhydride.

Accordingly, it is appreciated that, e.g., the term “butylsuccinicanhydride” comprises linear and branched butylsuccinic anhydride(s). Onespecific example of linear butylsuccinic anhydride(s) is n-butylsuccinicanhydride. Other specific examples of branched butylsuccinicanhydride(s) are iso-butylsuccinic anhydride, sec-butylsuccinicanhydride and/or tert-butylsuccinic anhydride.

Furthermore, it is appreciated that e.g. the term “hexadecanyl succinicanhydride” comprises linear and branched hexadecanyl succinicanhydride(s). One specific example of linear hexadecanyl succinicanhydride(s) is n-hexadecanyl succinic anhydride. Other specificexamples of branched hexadecanyl succinic anhydride(s) are14-methylpentadecanyl succinic anhydride, 13-methylpentadecanyl succinicanhydride, 12-methylpentadecanyl succinic anhydride,11-methylpentadecanyl succinic anhydride, 10-methylpentadecanyl succinicanhydride, 9-methylpentadecanyl succinic anhydride, 8-methylpentadecanylsuccinic anhydride, 7-methylpentadecanyl succinic anhydride,6-methylpentadecanyl succinic anhydride, 5-methylpentadecanyl succinicanhydride, 4-methylpentadecanyl succinic anhydride, 3-methylpentadecanylsuccinic anhydride, 2-methylpentadecanyl succinic anhydride,1-methylpentadecanyl succinic anhydride, 13-ethylbutadecanyl succinicanhydride, 12-ethylbutadecanyl succinic anhydride, 11-ethylbutadecanylsuccinic anhydride, 10-ethylbutadecanyl succinic anhydride,9-ethylbutadecanyl succinic anhydride, 8-ethylbutadecanyl succinicanhydride, 7-ethylbutadecanyl succinic anhydride, 6-ethylbutadecanylsuccinic anhydride, 5-ethylbutadecanyl succinic anhydride,4-ethylbutadecanyl succinic anhydride, 3-ethylbutadecanyl succinicanhydride, 2-ethylbutadecanyl succinic anhydride, 1-ethylbutadecanylsuccinic anhydride, 2-butyldodecanyl succinic anhydride, 1-hexyldecanylsuccinic anhydride, 1-hexyl-2-decanyl succinic anhydride, 2-hexyldecanylsuccinic anhydride, 6,12-dimethylbutadecanyl succinic anhydride,2,2-diethyldodecanyl succinic anhydride, 4,8,12-trimethyltridecanylsuccinic anhydride, 2,2,4,6,8-pentamethylundecanyl succinic anhydride,2-ethyl-4-methyl-2-(2-methylpentyl)-heptyl succinic anhydride and/or2-ethyl-4,6-dimethyl-2-propylnonyl succinic anhydride.

Furthermore, it is appreciated that, e.g., the term “octadecanylsuccinic anhydride” comprises linear and branched octadecanyl succinicanhydride(s). One specific example of linear octadecanyl succinicanhydride(s) is n-octadecanyl succinic anhydride. Specific examples ofbranched hexadecanyl succinic anhydride(s) are 16-methylheptadecanylsuccinic anhydride, 15-methylheptadecanyl succinic anhydride,14-methylheptadecanyl succinic anhydride, 13-methylheptadecanyl succinicanhydride, 12-methylheptadecanyl succinic anhydride,11-methylheptadecanyl succinic anhydride, 10-methylheptadecanyl succinicanhydride, 9-methylheptadecanyl succinic anhydride, 8-methylheptadecanylsuccinic anhydride, 7-methylheptadecanyl succinic anhydride,6-methylheptadecanyl succinic anhydride, 5-methylheptadecanyl succinicanhydride, 4-methylheptadecanyl succinic anhydride, 3-methylheptadecanylsuccinic anhydride, 2-methylheptadecanyl succinic anhydride,1-methylheptadecanyl succinic anhydride, 14-ethylhexadecanyl succinicanhydride, 13-ethylhexadecanyl succinic anhydride, 12-ethylhexadecanylsuccinic anhydride, 11-ethylhexadecanyl succinic anhydride,10-ethylhexadecanyl succinic anhydride, 9-ethylhexadecanyl succinicanhydride, 8-ethylhexadecanyl succinic anhydride, 7-ethylhexadecanylsuccinic anhydride, 6-ethylhexadecanyl succinic anhydride,5-ethylhexadecanyl succinic anhydride, 4-ethylhexadecanyl succinicanhydride, 3-ethylhexadecanyl succinic anhydride, 2-ethylhexadecanylsuccinic anhydride, 1-ethylhexadecanyl succinic anhydride,2-hexyldodecanyl succinic anhydride, 2-heptylundecanyl succinicanhydride, iso-octadecanyl succinic anhydride and/or 1-octyl-2-decanylsuccinic anhydride.

In one embodiment of the present invention, the at least one alkylmonosubstituted succinic anhydride is selected from the group consistingof butylsuccinic anhydride, hexylsuccinic anhydride, heptylsuccinicanhydride, octylsuccinic anhydride, hexadecanyl succinic anhydride, andoctadecanyl succinic anhydride.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is one kind of alkyl monosubstitutedsuccinic anhydride. For example, the one alkyl monosubstituted succinicanhydride is butylsuccinic anhydride. Alternatively, the one alkylmonosubstituted succinic anhydride is hexylsuccinic anhydride.Alternatively, the one alkyl monosubstituted succinic anhydride isheptylsuccinic anhydride or octylsuccinic anhydride. Alternatively, theone alkyl monosubstituted succinic anhydride is hexadecanyl succinicanhydride. For example, the one alkyl monosubstituted succinic anhydrideis linear hexadecanyl succinic anhydride such as n-hexadecanyl succinicanhydride or branched hexadecanyl succinic anhydride such as1-hexyl-2-decanyl succinic anhydride. Alternatively, the one alkylmonosubstituted succinic anhydride is octadecanyl succinic anhydride.For example, the one alkyl monosubstituted succinic anhydride is linearoctadecanyl succinic anhydride such as n-octadecanyl succinic anhydrideor branched octadecanyl succinic anhydride such as iso-octadecanylsuccinic anhydride or 1-octyl-2-decanyl succinic anhydride.

In one embodiment of the present invention, the one alkylmonosubstituted succinic anhydride is butylsuccinic anhydride such asn-butylsuccinic anhydride.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is a mixture of two or more kinds ofalkyl monosubstituted succinic anhydrides. For example, the at least onemonosubstituted succinic anhydride is a mixture of two or three kinds ofalkyl monosubstituted succinic anhydrides.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride consists of succinic anhydridemonosubstituted with one group being a linear or branched alkenyl grouphaving a total amount of carbon atoms from C2 to C30, preferably from C3to C20, and most preferably from C4 to C18 in the substituent.

The term “alkenyl” in the meaning of the present invention refers to alinear or branched unsaturated organic compound composed of carbon andhydrogen. Said organic compound further contains at least one doublebond in the substituent, preferably one double bond. In other words,“alkenyl monosubstituted succinic anhydrides” are composed of linear orbranched unsaturated hydrocarbon chains containing a pendant succinicanhydride group. It is appreciated that the term “alkenyl” in themeaning of the present invention includes both the cis and transisomers.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is at least one linear or branchedalkenyl monosubstituted succinic anhydride. For example, the at leastone alkenyl monosubstituted succinic anhydride is selected from thegroup consisting of ethenylsuccinic anhydride, propenylsuccinicanhydride, butenylsuccinic anhydride, triisobutenyl succinic anhydride,pentenylsuccinic anhydride, hexenylsuccinic anhydride, heptenylsuccinicanhydride, octenylsuccinic anhydride, nonenylsuccinic anhydride, decenylsuccinic anhydride, dodecenyl succinic anhydride, hexadecenyl succinicanhydride, and octadecenyl succinic anhydride.

Accordingly, it is appreciated that, e.g., the term “hexadecenylsuccinic anhydride” comprises linear and branched hexadecenyl succinicanhydride(s). One specific example of linear hexadecenyl succinicanhydride(s) is n-hexadecenyl succinic anhydride such as 14-hexadecenylsuccinic anhydride, 13-hexadecenyl succinic anhydride, 12-hexadecenylsuccinic anhydride, 11-hexadecenyl succinic anhydride, 10-hexadecenylsuccinic anhydride, 9-hexadecenyl succinic anhydride, 8-hexadecenylsuccinic anhydride, 7-hexadecenyl succinic anhydride, 6-hexadecenylsuccinic anhydride, 5-hexadecenyl succinic anhydride, 4-hexadecenylsuccinic anhydride, 3-hexadecenyl succinic anhydride and/or2-hexadecenyl succinic anhydride. Specific examples of branchedhexadecenyl succinic anhydride(s) are 14-methyl-9-pentadecenyl succinicanhydride, 14-methyl-2-pentadecenyl succinic anhydride,1-hexyl-2-decenyl succinic anhydride and/or iso-hexadecenyl succinicanhydride.

Furthermore, it is appreciated that e.g. the term “octadecenyl succinicanhydride” comprises linear and branched octadecenyl succinicanhydride(s). One specific example of linear octadecenyl succinicanhydride(s) is n-octadecenyl succinic anhydride such as 16-octadecenylsuccinic anhydride, 15-octadecenyl succinic anhydride, 14-octadecenylsuccinic anhydride, 13-octadecenyl succinic anhydride, 12-octadecenylsuccinic anhydride, 11-octadecenyl succinic anhydride, 10-octadecenylsuccinic anhydride, 9-octadecenyl succinic anhydride, 8-octadecenylsuccinic anhydride, 7-octadecenyl succinic anhydride, 6-octadecenylsuccinic anhydride, 5-octadecenyl succinic anhydride, 4-octadecenylsuccinic anhydride, 3-octadecenyl succinic anhydride and/or2-octadecenyl succinic anhydride. Specific examples of branchedoctadecenyl succinic anhydride(s) are 16-methyl-9-heptadecenyl succinicanhydride, 16-methyl-7-heptadecenyl succinic anhydride,1-octyl-2-decenyl succinic anhydride and/or iso-octadecenyl succinicanhydride.

In one embodiment of the present invention, the at least one alkenylmonosubstituted succinic anhydride is selected from the group consistingof hexenylsuccinic anhydride, octenylsuccinic anhydride, hexadecenylsuccinic anhydride, and octadecenyl succinic anhydride.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is one alkenyl monosubstitutedsuccinic anhydride. For example, the one alkenyl monosubstitutedsuccinic anhydride is hexenylsuccinic anhydride. Alternatively, the onealkenyl monosubstituted succinic anhydride is octenylsuccinic anhydride.Alternatively, the one alkenyl monosubstituted succinic anhydride ishexadecenyl succinic anhydride. For example, the one alkenylmonosubstituted succinic anhydride is linear hexadecenyl succinicanhydride such as n-hexadecenyl succinic anhydride or branchedhexadecenyl succinic anhydride such as 1-hexyl-2-decenyl succinicanhydride. Alternatively, the one alkenyl monosubstituted succinicanhydride is octadecenyl succinic anhydride. For example, the one alkylmonosubstituted succinic anhydride is linear octadecenyl succinicanhydride such as n-octadecenyl succinic anhydride or branchedoctadecenyl succinic anhydride such iso-octadecenyl succinic anhydride,or 1-octyl-2-decenyl succinic anhydride.

In one embodiment of the present invention, the one alkenylmonosubstituted succinic anhydride is linear octadecenyl succinicanhydride such as n-octadecenyl succinic anhydride. In anotherembodiment of the present invention, the one alkenyl monosubstitutedsuccinic anhydride is linear octenylsuccinic anhydride such asn-octenylsuccinic anhydride.

If the at least one monosubstituted succinic anhydride is one alkenylmonosubstituted succinic anhydride, it is appreciated that the onealkenyl monosubstituted succinic anhydride is present in an amount of atleast 95.0 wt.-% and preferably of at least 96.5 wt.-%, based on thetotal weight of the at least one monosubstituted succinic anhydride ofstep (e).

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is a mixture of two or more kinds ofalkenyl monosubstituted succinic anhydrides. For example, the at leastone monosubstituted succinic anhydride is a mixture of two or threekinds of alkenyl monosubstituted succinic anhydrides.

If the at least one monosubstituted succinic anhydride is a mixture oftwo or more kinds of alkenyl monosubstituted succinic anhydrides, onealkenyl monosubstituted succinic anhydride is linear or branchedoctadecenyl succinic anhydride, while each further alkenylmonosubstituted succinic anhydride is selected from ethenylsuccinicanhydride, propenylsuccinic anhydride, butenylsuccinic anhydride,pentenylsuccinic anhydride, hexenylsuccinic anhydride, heptenylsuccinicanhydride, nonenylsuccinic anhydride, hexadecenyl succinic anhydride,and mixtures thereof. For example, the at least one monosubstitutedsuccinic anhydride is a mixture of two or more kinds of alkenylmonosubstituted succinic anhydrides, wherein one alkenyl monosubstitutedsuccinic anhydride is linear octadecenyl succinic anhydride and eachfurther alkenyl monosubstituted succinic anhydride is selected fromethenylsuccinic anhydride, propenylsuccinic anhydride, butenylsuccinicanhydride, pentenylsuccinic anhydride, hexenylsuccinic anhydride,heptenylsuccinic anhydride, nonenylsuccinic anhydride, hexadecenylsuccinic anhydride, and mixtures thereof. Alternatively, the at leastone monosubstituted succinic anhydride is a mixture of two or more kindsof alkenyl monosubstituted succinic anhydrides, wherein one alkenylmonosubstituted succinic anhydride is branched octadecenyl succinicanhydride and each further alkenyl monosubstituted succinic anhydride isselected from ethenylsuccinic anhydride, propenylsuccinic anhydride,butenylsuccinic anhydride, pentenylsuccinic anhydride, hexenylsuccinicanhydride, heptenylsuccinic anhydride, nonenylsuccinic anhydride,hexadecenyl succinic anhydride, and mixtures thereof.

For example, the at least one monosubstituted succinic anhydride is amixture of two or more kinds of alkenyl monosubstituted succinicanhydrides comprising one or more hexadecenyl succinic anhydride, likelinear or branched hexadecenyl succinic anhydride(s), and one or moreoctadecenyl succinic anhydride, like linear or branched octadecenylsuccinic anhydride(s).

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is a mixture of two or more kinds ofalkenyl monosubstituted succinic anhydrides comprising linearhexadecenyl succinic anhydride(s) and linear octadecenyl succinicanhydride(s). Alternatively, the at least one monosubstituted succinicanhydride is a mixture of two or more kinds of alkenyl monosubstitutedsuccinic anhydrides comprising branched hexadecenyl succinicanhydride(s) and branched octadecenyl succinic anhydride(s). Forexample, the one or more hexadecenyl succinic anhydride is linearhexadecenyl succinic anhydride like n-hexadecenyl succinic anhydrideand/or branched hexadecenyl succinic anhydride like 1-hexyl-2-decenylsuccinic anhydride. Additionally or alternatively, the one or moreoctadecenyl succinic anhydride is linear octadecenyl succinic anhydridelike n-octadecenyl succinic anhydride and/or branched octadecenylsuccinic anhydride like iso-octadecenyl succinic anhydride and/or1-octyl-2-decenyl succinic anhydride.

If the at least one monosubstituted succinic anhydride is a mixture oftwo or more kinds of alkenyl monosubstituted succinic anhydrides, it isappreciated that one alkenyl monosubstituted succinic anhydride ispresent in an amount of from 20.0 to 60.0 wt.-% and preferably of from30.0 to 50.0 wt.-%, based on the total weight of the at least onemonosubstituted succinic anhydride of step (e).

For example, if the at least one monosubstituted succinic anhydride is amixture of two or more kinds of alkenyl monosubstituted succinicanhydrides comprising one or more hexadecenyl succinic anhydride(s),like linear or branched hexadecenyl succinic anhydride(s), and one ormore octadecenyl succinic anhydride(s), such as linear or branchedhexadecenyl succinic anhydride(s), it is preferred that the one or moreoctadecenyl succinic anhydride(s) is present in an amount of from 20.0to 60.0 wt.-% and preferably of from 30.0 to 50.0 wt.-%, based on thetotal weight of the at least one monosubstituted succinic anhydride ofstep (e).

It is also appreciated that the at least one monosubstituted succinicanhydride may be a mixture of at least one alkyl monosubstitutedsuccinic anhydrides and at least one alkenyl monosubstituted succinicanhydrides.

If the at least one monosubstituted succinic anhydride is a mixture ofat least one alkyl monosubstituted succinic anhydrides and at least onealkenyl monosubstituted succinic anhydrides, it is appreciated that thealkyl substituent of the of at least one alkyl monosubstituted succinicanhydrides and the alkenyl substituent of the of at least one alkenylmonosubstituted succinic anhydrides are preferably the same. Forexample, the at least one monosubstituted succinic anhydride is amixture of ethylsuccinic anhydride and ethenylsuccinic anhydride.Alternatively, the at least one monosubstituted succinic anhydride is amixture of propylsuccinic anhydride and propenylsuccinic anhydride.Alternatively, the at least one monosubstituted succinic anhydride is amixture of butylsuccinic anhydride and butenylsuccinic anhydride.Alternatively, the at least one monosubstituted succinic anhydride is amixture of triisobutyl succinic anhydride and triisobutenyl succinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of pentylsuccinic anhydride and pentenylsuccinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of hexylsuccinic anhydride and hexenylsuccinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of heptylsuccinic anhydride and heptenylsuccinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of octylsuccinic anhydride and octenylsuccinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of nonylsuccinic anhydride and nonenylsuccinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of decyl succinic anhydride and decenyl succinicanhydride. Alternatively, the at least one monosubstituted succinicanhydride is a mixture of dodecyl succinic anhydride and dodecenylsuccinic anhydride. Alternatively, the at least one monosubstitutedsuccinic anhydride is a mixture of hexadecanyl succinic anhydride andhexadecenyl succinic anhydride. For example, the at least onemonosubstituted succinic anhydride is a mixture of linear hexadecanylsuccinic anhydride and linear hexadecenyl succinic anhydride or amixture of branched hexadecanyl succinic anhydride and branchedhexadecenyl succinic anhydride. Alternatively, the at least onemonosubstituted succinic anhydride is a mixture of octadecanyl succinicanhydride and octadecenyl succinic anhydride. For example, the at leastone monosubstituted succinic anhydride is a mixture of linearoctadecanyl succinic anhydride and linear octadecenyl succinic anhydrideor a mixture of branched octadecanyl succinic anhydride and branchedoctadecenyl succinic anhydride.

In one embodiment of the present invention, the at least onemonosubstituted succinic anhydride is a mixture of nonylsuccinicanhydride and nonenylsuccinic anhydride.

If the at least one monosubstituted succinic anhydride is a mixture ofat least one alkyl monosubstituted succinic anhydrides and at least onealkenyl monosubstituted succinic anhydrides, the weight ratio betweenthe at least one alkyl monosubstituted succinic anhydride and the atleast one alkenyl monosubstituted succinic anhydride is between 90:10and 10:90. For example, the weight ratio between the at least one alkylmonosubstituted succinic anhydride and the at least one alkenylmonosubstituted succinic anhydride is between 70:30 and 30:70 or between60:40 and 40:60.

Optionally, at least one monosubstituted succinic acid and/or salt(s)thereof are provided according to step (e) of the inventive process.

It is appreciated that the expression “at least one” monosubstitutedsuccinic acid means that one or more kinds of monosubstituted succinicacid may be provided in the process of the present invention.

Accordingly, it should be noted that the at least one monosubstitutedsuccinic acid may be one kind of monosubstituted succinic acid.Alternatively, the at least one monosubstituted succinic acid may be amixture of two or more kinds of monosubstituted succinic acid. Forexample, the at least one monosubstituted succinic acid may be a mixtureof two or three kinds of monosubstituted succinic acid, like two kindsof monosubstituted succinic acid.

In one embodiment of the present invention, the at least onemonosubstituted succinic acid is one kind of monosubstituted succinicacid.

It is appreciated that the at least one monosubstituted succinic acidrepresents a surface treatment agent and consists of succinic acidmonosubstituted with an aliphatic group having a total amount of carbonatoms from C2 to C30 in the substituent.

In one embodiment of the present invention, the at least onemonosubstituted succinic acid consists of succinic acid monosubstitutedwith an aliphatic group having a total amount of carbon atoms from C3 toC20 in the substituent. For example, the at least one monosubstitutedsuccinic acid consists of succinic acid monosubstituted with analiphatic group having a total amount of carbon atoms from C4 to C18 inthe substituent.

It is appreciated that the at least one monosubstituted succinicanhydride and the at least one monosubstituted succinic acid maycomprise the same or different substituent.

In one embodiment of the present invention, the succinic acid moleculeof the at least one monosubstituted succinic acid and the succinicanhydride molecule of the at least one monosubstituted succinicanhydride are monosubstituted with the same group selected from analiphatic group having a total amount of carbon atoms from C2 to C30,preferably from C3 to C20 and most preferably from C4 to C18 in thesubstituent.

If the at least one monosubstituted succinic anhydride is provided incombination with at least one monosubstituted succinic acid and/orsalt(s) thereof, the at least one monosubstituted succinic acid and/orsalt(s) thereof are present in an amount of less than 10.0 mol-%, basedon the molar sum of the at least one monosubstituted succinic anhydrideand the at least one monosubstituted succinic acid and/or salt(s)thereof. For example, the at least one monosubstituted succinic acidand/or salt(s) thereof are present in an amount of less than 5.0 mol-%,preferably less than 2.5 mol-%, and most preferably less than 1.0 mol-%,based on the molar sum of the at least one monosubstituted succinicanhydride and the at least one monosubstituted succinic acid and/orsalt(s) thereof.

In one embodiment of the present invention, at least one monosubstitutedsuccinic anhydride and at least one monosubstituted succinic acid and/orsalt(s) thereof are used in the treatment step (e).

In the meaning of the present invention, salt(s) of the at least onemonosubstituted succinic acid may be lithium, sodium, potassium,strontium, calcium, magnesium, and/or aluminum salt(s).

If at least one monosubstituted succinic anhydride and at least onemonosubstituted succinic acid and/or salt(s) thereof are both used instep (e), the at least one monosubstituted succinic anhydride and the atleast one monosubstituted succinic acid and/or salt(s) thereof arepreferably provided as a blend.

Another requirement of the process according to the present invention isthe total amount of the at least one monosubstituted succinic anhydrideand the optional at least one monosubstituted succinic acid and/orsalt(s) thereof used in treatment step (e). In general, said totalamount may range from 0.01 to 10.0 wt.-%, based on the total dry weightof the calcium carbonate-containing material provided in step (a).

However, in order to reduce the total consumption of additives, it maybe preferred to use a relatively small total amount of said at least onemonosubstituted succinic anhydride and the optional at least onemonosubstituted succinic acid and/or salt(s) thereof. Therefore, in oneembodiment, the total amount of the at least one monosubstitutedsuccinic anhydride and the optional at least one monosubstitutedsuccinic acid and/or salt(s) thereof in step (e) may range from 0.01 to5.0 wt.-%, based on the total dry weight of the calciumcarbonate-containing material provided in step (a).

In another embodiment of the inventive process, the total amount of theat least one monosubstituted succinic anhydride and the optional atleast one monosubstituted succinic acid and/or salt(s) thereof in step(e) ranges from 0.05 to 3.0 wt.-%, preferably from 0.1 to 2.0 wt.-%, andmore preferably from 0.15 to 1.5 wt.-%, based on the total dry weight ofthe calcium carbonate-containing material provided in step (a).

Additionally or alternatively, it is to be noted that the at least onemonosubstituted succinic anhydride and the optional at least onemonosubstituted succinic acid of step (e) are liquid if provided at roomtemperature, i.e. said at least one monosubstituted succinic anhydridefeatures a viscosity of less than 5'000 mPa·s, preferably of less than2'500 mPa·s, more preferably of less than 1'000 mPa·s, and mostpreferably of less than 500 mPa·s at +20° C. (±2° C.), when measuredwith the appropriate equipment, e.g., Physica MCR 300 rheometer (PaarPhysica) equipped with the measuring cell TEZ 150 P-C and the CC 28.7measuring system at a shear rate of 5 s⁻¹ and at +20° C. (±2° C.).

Furthermore, the temperature at the beginning and also during treatmentstep (e) was found to be crucial in order to achieve the desiredtreatment results. Therefore, the temperature in treatment step (e) isadjusted to at least 2° C. above the melting point of the at least onemonosubstituted succinic anhydride in order to achieve sufficientdistribution of the treatment agent upon contacting same with thecalcium carbonate-containing material.

In all cases where more than one monosubstituted succinic anhydride isused, the temperature in treatment step (e) may be adjusted to at least2° C. above the melting point of the one having the highest meltingpoint.

It has been found that optimal treatment results can also be achievedwhen the temperature in step (e) is adjusted to at least 2° C. above themelting point of the at least one monosubstituted succinic anhydride foronly a limited period of time, for example, for less than 1 h,preferably less than 5 min, more preferably less than 1 min, and mostpreferably 1 to 10 s.

In a preferred embodiment, the temperature in step (e) is adjusted to atleast 2° C. above the melting point of the at least one monosubstitutedsuccinic anhydride for less than 1 h, preferably less than 5 min, morepreferably less than 1 min, and most preferably 1 to 10 s directly aftercontacting the calcium carbonate-containing material with the at leastone monosubstituted succinic anhydride and the optional at least onemonosubstituted succininc acid and/or salt(s) thereof.

Additionally or alternatively, the temperature during the entiretreatment step (e) lies within a certain range in order to achieve thedesired treatment results, wherein said range also includes thetemperature as described herein above with respect to the melting pointof the at least one monosubstituted succinic anhydride. Therefore, insome embodiments of the process according to the present invention, thetemperature during step (e) ranges from 30° C. to 200° C., preferablyfrom 80° C. to 150° C., and more preferably from 110° C. to 130° C.

In another embodiment of the process according to the present invention,the calcium carbonate-containing material is preheated to thetemperature defined in treatment step (e) for 1 to 30 min, preferably 2to 20 min, and most preferably 5 to 15 min before contacting, intreatment step (e), the calcium carbonate-containing material with theat least one monosubstituted succinic anhydride and the optional atleast one monosubstituted succinic acid and/or salt(s) thereof. In thisrespect, the temperature defined in step (e) may be a temperature of atleast 2° C. above the melting point of the at least one monosubstitutedsuccinic anhydride. The temperature adjusted by preheating may rangefrom 30° C. to 200° C., preferably from 80° C. to 150° C., and morepreferably from 110° C. to 130° C.

Depending on the order of steps, the preheating can be achieved by usingthe heat developed during dry grinding step (c). Additionally oralternatively, the preheating can be carried out in a separate step, forexample in a mixer which may also be used to carry out treatment step(e).

To achieve an optimal treatment, it is also possible to store thesurface-treated calcium carbonate-containing material at elevatedtemperatures for several hours or days, for example in a silo.

The present step of treating the calcium carbonate-containing materialwith at least one monosubstituted succinic anhydride and, optionally,with at least one monosubstituted succinic acid and/or salt(s) thereofmay be carried out before and/or during and/or after dry grinding step(c).

According to one embodiment, the treatment step is carried out duringand/or after dry grinding step (c).

During dry grinding the calcium carbonate-containing material in step(c), the grinding stock may become warm. Therefore, in cases where thetreatment step (e) is carried during or after grinding step (c), thewarming of the grinding stock may be used to adjust the temperaturesrequired for an optimal treatment according to process step (e).Independently from whether said treatment is carried out before, duringor after grinding step (c), it is possible to add the at least onemonosubstituted succinic anhydride and the optional at least onemonosubstituted succinic acid and/or salt(s) thereof in one or moreportions.

In cases where the treatment step is carried out during and after drygrinding, a first portion of the at least one monosubstituted succinicanhydride and the optional at least one monosubstituted succinic acidand/or salt(s) thereof are added to the mixture of step (c) and a secondportion of the at least one monosubstituted succinic anhydride and theoptional at least one monosubstituted succinic acid and/or salt(s)thereof are contacted with the calcium carbonate-containing material ina separate treatment step after grinding step (c).

According to another embodiment, treatment step (e) is carried out afterdry grinding step (c).

It has to be noted that in all cases where said treatment step iscarried out after dry grinding the calcium carbonate-containingmaterial, it is generally possible to carry out said treatment stepbefore or after classifying step (d). In the latter case, treatment step(e) represents the final process step yielding the mineral fillerproduct according to the present invention.

Therefore, according to one embodiment, treatment step (e) may becarried out after dry grinding step (c) and before classifying step (d).Alternatively, treatment step (e) may be carried out after dry grindingstep (c) and after classifying step (d).

The Mineral Filler Product

In the meaning of the present application, the inventive mineral fillerproduct is a calcium carbonate-containing material which has beensubjected to steps (a) to (e) as defined herein in the independentprocess claim. As already described above, said mineral filler productmay be obtained after classifying step (d) or after treatment step (e),depending on the order of steps.

It was found that the use of at least one agent being a polyol duringdry grinding step (c) may result in higher mill capacities and a higherthroughput which requires lower investments and smaller plant footprintsfor equal production capacities while, simultaneously, the treatmentlayer formed in treatment step (e) was found to be of particularadvantage with regard to the moisture pick up of the inventive mineralfiller product.

The moisture pick up (measured as the moisture pickup susceptibility) ofthe inventive mineral filler product may be very low and can beexpressed relative to a sample weight.

According to one embodiment, the mineral filler product has a moisturepick up susceptibility of less than or equal to 15.0 mg/g, preferablyless than or equal to 12.0 mg/g, more preferably less than or equal to8.0 mg/g, and most preferably less than or equal to 6.0 mg/g, whereinthe moisture pick up susceptibility preferably has a lower limit of 0.1mg/g.

According to another embodiment, the mineral filler product has amoisture pick up susceptibility ranging from 0.1 to 15.0 mg/g,preferably from 0.2 to 12.0 mg/g, more preferably from 0.5 to 10.0 mg/g,and most preferably from 0.6 to 8.0 mg/g.

In some particular cases as, for example, in case of high specificsurface areas of the mineral filler product, the moisture pick upsusceptibility may be suitably defined based on the specific surfacearea of said product (referred to as the normalized moisture pick upsusceptibility).

According to one embodiment, the mineral filler product has a normalizedmoisture pick up susceptibility of less than or equal to 1.5 mg/m²,preferably less than or equal to 1.0 mg/m², more preferably less than orequal to 0.5 mg/m², and most preferably less than or equal to 0.25mg/m², based on the specific surface area of said product as measured bythe BET nitrogen method, wherein the normalized moisture pick upsusceptibility preferably has a lower limit of 0.01 mg/m², based on thespecific surface area as measured by the BET nitrogen method.

The mineral filler product obtainable according to the present inventionmay have a specific surface area ranging from 0.5 to 20.0 m²/g,preferably from 1.0 to 10.0 m²/g, and more preferably from 2.0 to 8.0m²/g as measured by the BET nitrogen method.

The mineral filler product of the present invention can also becharacterized by its particle size distribution.

In one embodiment, the mineral filler product has a weight medianparticle size d₅₀ ranging from 0.5 to 30.0 μm, preferably from 1.0 to15.0 μm, and more preferably from 1.5 to 12.0 μm.

According to another embodiment, the mineral filler product has a weightmedian particle size d₅₀ ranging from 0.3 to 25.0 μm, preferably from0.5 to 10.0 μm, more preferably from 1.0 to 8.0 μm, and most preferablyfrom 1.2 to 5.0 μm.

In addition or alternatively to the foregoing weight median particlesizes, the mineral filler product may have a particle size topcut d₉₈ranging from 1.5 to 50.0 μm, preferably from 2.0 to 30.0 μm, and morepreferably from 2.5 to 15.0 μm.

In treatment step (e), a treatment layer is formed on at least part ofthe surface of the calcium carbonate-containing material. Therefore,said treatment layer may comprise the at least one monosubstitutedsuccinic anhydride and/or reaction product(s) thereof and the optionalat least one monosubstituted succinic acid and/or salt(s) thereof and/orreaction product(s) thereof in a total amount of from 0.01 to 2.0 wt.-%,preferably from 0.05 to 1.5 wt.-%, and more preferably from 0.1 to 1.0wt.-%, based on the total dry weight of the calcium carbonate-containingmaterial.

A “reaction product” in the meaning of the present invention is acompound resulting from the reaction of the at least one monosubstitutedsuccinic anhydride or the optional at least one monosubstituted succinicacid with the calcium carbonate-containing material. Typically, saidreaction product is a reaction product resulting from the reaction ofthe aforementioned treatment agents with the surface of the calciumcarbonate-containing material.

In many cases, the reaction products of the at least one monosubstitutedsuccinic anhydride or the optional at least one monosubstituted succinicacid are salty reaction products, e.g., lithium, sodium, potassium,strontium, calcium, magnesium and/or aluminum salts. The skilled personwill appreciate that many reaction products resulting from the reactionof a monosubstituted succinic anhydride may be identical to thoseresulting from the reaction of a corresponding monosubstituted succinicacid and/or salt(s) thereof.

It has been found that in order to achieve optimal treatment results, itis also possible to store the treated calcium carbonate-containingmaterial at elevated temperatures for several hours or days, for examplein a silo. Upon silo storage, unreacted treatment agent may react withthe calcium carbonate-containing material surface.

According to a further aspect, the inventive mineral filler product maybe used in a polymer composition, in paper making, paper coatings,agricultural applications, paints, adhesives, sealants, constructionapplications, and/or cosmetic applications, preferably said mineralfiller product is used in a polymer composition.

As the mineral filler product has a low moisture pick up susceptibility,it may advantageously be used in paper coatings in order to adjust theprinting properties of a coated paper. Furthermore, the mineral fillerproduct may also be used in exterior paints and bathroom paints whichmay lead to a reduction in mildew growth on surfaces being treated withsuch paints.

A number of the aforementioned applications (e.g., for coatings orpaints) involve the preparation of an aqueous slurry comprising themineral filler product obtainable by the process according to thepresent invention. Such aqueous slurries may be easily prepared from theinventive mineral filler product by the addition of water to obtainslurries having a solids content of, for example, from 10.0 to 85.0wt.-%, based on the total weight of said slurry.

The use of the mineral filler product according to the present inventionas a filler material in polymer applications may also be of particularadvantage. For example, said filler may be used in thermoplasticpolymers, such as polyvinyl chloride, polyolefins, and polystyrene whichmay allow an increased filler load as compared to conventional calciumcarbonate fillers.

The polymer composition of the present invention may also be used in anumber of processes including the manufacture of blown films, sheets, orpipe profiles, in processes such as extrusion of pipes, profiles,cables, filaments, fibres or the like, and in compression moulding,injection moulding, thermoforming, blow moulding, and rotationalmoulding, etc.

In this respect, said polymer composition may be directly used in themanufacture of polymer articles. In one embodiment of the presentinvention, the polymer composition comprises the mineral filler productin an amount of from 1.0 to 50.0 wt.-%, preferably of from 5.0 to 45.0wt.-%, and most preferably from 10.0 to 40.0 wt.-%, based on the totalweight of the polymer composition.

EXAMPLES

The scope and interest of the invention may be better understood onbasis of the following examples which are intended to illustrateembodiments of the present invention. However, they are not to beconstrued to limit the scope of the claims in any manner whatsoever.

Example 1

Marble from Carrara, Italy was wet ground at 25 wt.-% solids content intap water in a horizontal ball mill (Dynomill) and spray dried. Theobtained calcium carbonate-containing material features a d₅₀ ofapproximately 1.7 μm, a topcut (d₉₈) of 5.0 μm, a specific surface area(BET) of 4.1 m²/g, and a total moisture content of 0.06 wt.-%.

This dry calcium carbonate was used to demonstrate the effect of amonosubstituted succinic anhydride on the moisture pickup of a mineralfiller product. In order to simulate dry grinding in the presence ofglycerol, the dry calcium carbonate was treated with 0.6 wt.-% ofglycerol in a MTI mixer (MTI Mischtechnik International GmbH). Thecontents of the mixer were mixed at 120° C. under a stirring speed of3'000 rpm for a period of 10 min.

The glycerol-containing calcium carbonate was subsequently divided inseveral aliquots and surface-treated with either stearic acid oralkenylsuccinic anhydride (HYDRORES AS 1000, commercially available fromKemira Oyj, Vaasa, Finland) in the MTI mixer. The glycerol-containingcalcium carbonate was activated for 10 min at 120° C. and 3'000 rpm.Subsequently, the treatment agent was added and the blend was furthermixed at 120° C. at a stirring speed of 3'000 rpm for a period of 10min. The results are given in Table 1 below.

TABLE 1 Moisture pickup of dry ground calcium carbonate (n/d = notdetermined). Moisture pickup susceptibility [mg/g] Treatment agentStearic acid Succinic anhydride [wt.-%] (prior art) (inventive) 0.0 7.50.3 6.2 6.3 0.4 n/d 6.4 0.5 6.6 6.1 0.6 n/d 5.7 0.8 6.3 4.8 1.0 6.0 4.4

Example 2

The effect of a reduced moisture pick is also observed in cases wherethe calcium carbonate contains more than one polyol.

Marble from Carrara, Italy was dry ground in a ball mill equipped with aclassifier to produce a dry ground calcium carbonate with d₅₀ of 2 μm, atopcut (d₉₈) of 10 μm, and wherein 60 wt.-% of the particles have aparticle size of below 2 μm. The total moisture content was 0.3 wt %.For the dry grinding process, 1'500 ppm of a blend (weight ratio 80:20)of glycerol and triisopropanolamine was used as dry grinding agent.

The dry ground calcium carbonate was subsequently divided in severalaliquots and surface-treated with either stearic acid or alkenylsuccinicanhydride (HYDRORES AS 1000, commercially available from Kemira Oyj,Vaasa, Finland) in a MTI mixer (MTI Mischtechnik International GmbH).The dry ground calcium carbonate was activated for 10 min at 120° C. and3'000 rpm. Subsequently, the treatment agent was added and the blend wasfurther mixed at 120° C. at a stirring speed of 3'000 rpm for a periodof 10 min. The results are given in Table 2 below.

TABLE 2 Moisture pickup of dry ground calcium carbonate. Moisture pickupsusceptibility [mg/g] Treatment agent Stearic acid Succinic anhydride[wt.-%] (prior art) (inventive) 0.0 5.52 0.6 2.72 2.25 0.8 2.57 2.05

In both examples, a reduced moisture pickup as compared to prior arttreatment methods using stearic acid can be observed while usingglycerol as an agent being suitable to increase the grinding efficiencyand throughput.

1. A mineral filler product obtained by a process comprising the stepsof: (a) providing a calcium carbonate-containing material; (b) providingat least one agent being a polyol; (c) dry grinding the calciumcarbonate-containing material in a mixture comprising: (i) the calciumcarbonate-containing material provided in step (a); and (ii) the atleast one agent provided in step (b), in at least one grinding unit toobtain a dry ground calcium carbonate-containing material; (d)classifying the dry ground calcium carbonate-containing material of step(c) to obtain one or more coarse fractions and one or more finefractions, wherein one or more of the coarse fractions are removedand/or subjected to dry grinding step (c) and/or subjected toclassifying step (d); and (e) treating the calcium carbonate-containingmaterial before and/or during and/or after step (c) with at least onemonosubstituted succinic anhydride and, optionally, with at least onemonosubstituted succinic acid and/or salts thereof to obtain a calciumcarbonate-containing material having a treatment layer on at least partof the surface of said material; wherein the total amount of the atleast one agent provided in step (b) ranges from 0.01 to 5.0 wt.-%,based on the total dry weight of the calcium carbonate-containingmaterial provided in step (a); the total moisture content in the mixtureof step (c) is less than or equal to 5.0 wt.-%, based on the totalweight of said mixture; the total amount of the at least onemonosubstituted succinic anhydride and the optional at least onemonosubstituted succinic acid and/or salts thereof in step (e) rangesfrom 0.01 to 5.0 wt.-%, based on the total dry weight of the calciumcarbonate-containing material provided in step (a); and the temperaturein step (e) is adjusted to at least 2° C. above the melting point of theat least one monosubstituted succinic anhydride.
 2. The mineral fillerproduct according to claim 1, having a weight median particle size d₅₀ranging from 0.3 to 25.0 μm.
 3. The mineral filler product according toclaim 1, having a weight median particle size d₅₀ ranging from 1.2 to5.0 μm.
 4. The mineral filler product according to claim 1, having aspecific surface area ranging from 0.5 to 20.0 m²/g as measured by theBET nitrogen method.
 5. The mineral filler product according to claim 1,having a specific surface area ranging from 1.0 to 10.0 m²/g as measuredby the BET nitrogen method.
 6. The mineral filler product according toclaim 1, wherein the calcium carbonate-containing material provided instep (a) is obtained from a natural calcium carbonate source.
 7. Themineral filler product according to claim 1, wherein the calciumcarbonate-containing material is calcite, marble, limestone, chalk,dolomite, or any mixture thereof.
 8. The mineral filler productaccording to claim 1, wherein the at least one agent provided in step(b) is a polyol selected from the group consisting of a saccharide,glycerol, polyglycerol, ethylene glycol, propylene glycol, oligomers andpolymers of ethylene glycol and/or propylene glycol, andtriisopropanolamine.
 9. The mineral filler product according to claim 1,wherein the at least one agent is a polyol selected from glycerol andtriisopropanolamine.
 10. The mineral filler product according to claim1, wherein the total amount of the at least one agent provided in step(b) ranges from 0.05 to 3.0 wt.-%, based on the total dry weight of thecalcium carbonate-containing material provided in step (a).
 11. Themineral filler product according to claim 1, wherein the total moisturecontent in the mixture of step (c) is less than or equal to 2.0 wt.-%,based on the total weight of said mixture.
 12. The mineral fillerproduct according to claim 1, wherein the total moisture content in themixture of step (c) is less than or equal to 1.0 wt.-%, based on thetotal weight of said mixture.
 13. The mineral filler product accordingto claim 1, wherein the at least one monosubstituted succinic anhydrideof step (e) consists of succinic anhydride monosubstituted with analiphatic group having a total amount of carbon atoms from C2 to C30.14. The mineral filler product according to claim 1, wherein the atleast one monosubstituted succinic anhydride of step (e) consists ofsuccinic anhydride monosubstituted with an aliphatic group having atotal amount of carbon atoms from C3 to C25.
 15. The mineral fillerproduct according to claim 1, wherein the at least one monosubstitutedsuccinic anhydride of step (e) consists of succinic anhydridemonosubstituted with an aliphatic group having a total amount of carbonatoms from C4 to C20.
 16. The mineral filler product according to claim1, wherein the at least one monosubstituted succinic anhydride of step(e) is at least one alkyl monosubstituted succinic anhydride.
 17. Themineral filler product according to claim 1, wherein the at least onemonosubstituted succinic anhydride of step (e) is at least one alkylmonosubstituted succinic anhydride selected from the group consisting ofethylsuccinic anhydride, propylsuccinic anhydride, butylsuccinicanhydride, triisobutyl succinic anhydride, pentylsuccinic anhydride,hexylsuccinic anhydride, heptylsuccinic anhydride, octylsuccinicanhydride, nonylsuccinic anhydride, decyl succinic anhydride, dodecylsuccinic anhydride, hexadecanyl succinic anhydride, and octadecanylsuccinic anhydride.
 18. The mineral filler product according to claim 1,wherein the at least one monosubstituted succinic anhydride of step (e)is at least one alkenyl monosubstituted succinic anhydride.
 19. Themineral filler product according to claim 1, wherein the at least onemonosubstituted succinic anhydride of step (e) is at least one alkenylmonosubstituted succinic anhydride selected from the group consisting ofethenylsuccinic anhydride, propenylsuccinic anhydride, butenylsuccinicanhydride, triisobutenyl succinic anhydride, pentenylsuccinic anhydride,hexenylsuccinic anhydride, heptenylsuccinic anhydride, octenylsuccinicanhydride, nonenylsuccinic anhydride, decenyl succinic anhydride,dodecenyl succinic anhydride, hexadecenyl succinic anhydride, andoctadecenyl succinic anhydride.
 20. The mineral filler product accordingto claim 1, wherein the temperature during step (e) ranges from 30° C.to 200° C.
 21. The mineral filler product according to claim 1, whereinthe temperature in step (e) is adjusted to at least 2° C. above themelting point of the at least one monosubstituted succinic anhydride forless than 1 h.
 22. The mineral filler product according to claim 1,wherein the temperature in step (e) is adjusted to at least 2° C. abovethe melting point of the at least one monosubstituted succinic anhydridefor less than 5 min.
 23. The mineral filler product according to claim1, wherein the total amount of the at least one monosubstituted succinicanhydride and the optional at least one monosubstituted succinic acidand/or salts thereof in step (e) ranges from 0.05 to 3.0 wt.-%, based onthe total dry weight of the calcium carbonate-containing materialprovided in step (a).
 24. The mineral filler product according to claim1, wherein the total amount of the at least one monosubstituted succinicanhydride and the optional at least one monosubstituted succinic acidand/or salts thereof in step (e) ranges from 0.1 to 2.0 wt.-%, based onthe total dry weight of the calcium carbonate-containing materialprovided in step (a).
 25. The mineral filler product according to claim1, wherein the total amount of the at least one monosubstituted succinicanhydride and the optional at least one monosubstituted succinic acidand/or salts thereof in step (e) ranges from 0.15 to 1.5 wt.-%, based onthe total dry weight of the calcium carbonate-containing materialprovided in step (a).
 26. The mineral filler product according to claim1, wherein said treatment layer of step (e) comprises the at least onemonosubstituted succinic anhydride and/or reaction product(s) thereofand the optional at least one monosubstituted succinic acid and/or saltsthereof and/or reaction product(s) thereof in a total amount of from0.01 to 2.0 wt.-%, based on the total dry weight of the calciumcarbonate-containing material.
 27. The mineral filler product accordingto claim 1, wherein said treatment layer of step (e) comprises the atleast one monosubstituted succinic anhydride and/or reaction product(s)thereof and the optional at least one monosubstituted succinic acidand/or salts thereof and/or reaction product(s) thereof in a totalamount of from 0.05 to 1.5 wt.-%, based on the total dry weight of thecalcium carbonate-containing material.
 28. The mineral filler productaccording to claim 1, wherein said treatment layer of step (e) comprisesthe at least one monosubstituted succinic anhydride and/or reactionproduct(s) thereof and the optional at least one monosubstitutedsuccinic acid and/or salts thereof and/or reaction product(s) thereof ina total amount of from 0.1 to 1.0 wt.-%, based on the total dry weightof the calcium carbonate-containing material.